Beam Dynamics in High-intensity Linacs

Paper	Title	Page
MOP217	MEBT2 Design for the C-ADS Linac	93
	Z. Guo, H. Geng, Z. Li, J.Y. Tang IHEP, Beijing, People's Republic of China
	The C-ADS linac is composed by two parallel injectors and a main linac, a section of Medium Energy Beam Line (MEBT2) is designed to guide and match beams from two injectors to the main linac. The two injectors are hot-spare for each other in order to satisfied the requirement of high availability and reliability. The beam in online operation mode will be directed to the main linac from one injector, while the beam in the offline mode with low repetition frequency from the other injector, will be directed to a beam dump through an auxiliary beam line. With a long drift distance and in the presence of space charge force for 10 mA 10 MeV proton beam, the debunching effect is very strong and it requires very strict control over beam losses and emittance growth. It is difficult to obtain satisfactory longitudinal matching without bunchers in the bending section. An analytical study using transfer matrix shows that with two bunchers of same voltage in the bending section the achromatism can be maintained if the effective voltage is inversely proportional to the distance between the two bunchers. It is also under consideration if and how a beam collimation can be implanted in MEBT2.
MOP218	Dynamics of Particles in a Tilted Solenoidal Focusing Channel	97
	H. Jiang, S. Fu IHEP, Beijing, People's Republic of China
	We use the paraxial ray approximation equations to analysis the dynamics of particles in a tilted solenoidal focusing channel. In this case, the particles' initial canonical angular momentum is nonzero, so we need to add the term of centrifugal potential to the dynamics equation of particles. And in the dynamics equation this centrifugal potential term is nonlinear, which results in the emittance growth. In practice, we also need to consider the spherical aberration's effect on emittance growth and the linear part of the space-charge force of a Kapchinskij-Vladimirskij distribution beam in the dynamics equation of particles.
MOP219	Error Analysis and Correction Scheme in C-ADS Injector-I	99
	C. Meng, Z. Li, J.Y. Tang IHEP, Beijing, People's Republic of China
	Funding: Supported by the China ADS Project (XDA03020000) C-ADS Injector-I is a 10 mA 10 MeV CW proton linac. It uses a 3.2MeV normal conducting 4-Vane RFQ and 12 superconducting single-Spoke cavities. According to the detailed sensitivity analysis of alignment and RF errors, the error tolerance of both static and dynamic ones for Injector-I are presented. The simulation results show that with the error tolerance there are beam losses, the residual orbit is too large which will produce significant emittance growth, so the correction is necessary for Injector-I. After detailed numerical studies, a correction scheme and monitor distributions are proposed. After correction the RMS residual orbit can be controlled within 0.4mm and RMS emittance growth can be controlled within 10%, but it still has 1.7×10-6 beam loss, which comes from the RF errors and low longitudinal acceptance. According to detailed analysis and simulations with 108 macro particles, as a consequence, longitudinal emittance control and longitudinal distribution control as well as large longitudinal acceptance are the key to minimizing beam losses in low energy section. To minimize beam loss, a short period Injector-I lattice with larger longitudinal acceptance have been designed and performance very good error tolerance.
MOP220	Local Compensation-rematch for Major Element Failures in the C-ADS Accelerator	102
	B. Sun, Z. Li, J.Y. Tang, F. Yan IHEP, Beijing, People's Republic of China
	In order to achieve the required reliability and availability for the C-ADS accelerator, a fault tolerance design is pursued. The effects of cavity failure in different locations have been studied and the schemes of compensation by means of local compensation have been investigated. After one cavity failure, by adjusting the settings of the neighboring cavities and the focusing elements to make sure that the Twiss parameters and energy are approximately recovered to that of the nominal ones at the matching point. We find the normalized RMS emittance and emittances including 99.9% and 100% particles have no obvious growth after applying the compensation with the RMS rematching in each section of the main linac. However, the conclusions above are drawn from the simulation results with the TraceWin code, which doesn't consider the phase difference. A code based on Matlab is under developing. By applying the code on the cavity failure in the middle part of spoke021 section, a fully compensated scheme with good dynamics results is obtained. The space charge effect is still not implanted in the code, and further study and optimization of the code will be performed in the next step.
MOP221	Physics Design of the C-ADS Main Linac Based on Two Different Injector Design Schemes	107
	F. Yan, Z. Li, C. Meng, J.Y. Tang IHEP, Beijing, People's Republic of China
	Funding: Supported by Advanced Research Project of the Chinese Academy of Science Two design schemes for the main linac of C-ADS (China Accelerator Driven Subcritical system) are presented in this paper. They are corresponding to two different injector schemes. Injector-II scheme makes use of room-temperature RFQ and superconducting HWR cavities with the RF frequency of 162.5 MHz; Injector-I scheme makes use of higher-energy RFQ and superconducting spoke cavities with the RF frequency of 325 MHz. At the first choice, a relatively smaller longitudinal emittance is adopted for the RFQ designs with both the injector schemes to obtain more efficient acceleration. However, compared with the injector-I scheme, with the injector-II scheme, bunch current will be doubled in the main linac due to the half RF frequency in the injector-II. This means stronger space charge effects. Alternate design for the main linac with the injector-II scheme is to increase the longitudinal emittance by 50% so that the space charge effects will be alleviated. However, totally 30 cavities more and 36 m longer in the main linac have to be paid for this design scheme. The design considerations, the lattice designs, the simulation results including halo information are presented.
MOP229	Design of the MEBT1 for C-ADS Injector II	115
	H. Jia, Y. He, S.C. Huang, C.L. Luo, M.T. Song, Y.J. Yuan, X. Zhang IMP, Lanzhou, People's Republic of China
	The MEBT1 of Chinese ADS Injector II is described. It transports a 2.1 MeV, 10 mA CW proton beam through a series of 7 quadruples and two buncher cavities from the RFQ to the superconducting DTL. For emittance preservation, a compact mechanical design is required. Details of the beam dynamics and mechanical design will be given.
MOP231	Study of Non-equi-partitioning Lattice Setting and IBS Effects for J-PARC Linac Upgrade	118
	Y. Liu IMP, Lanzhou, People's Republic of China M. Ikegami JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	For the coming upgrade of J-Parc, the peak power of linac will be greatly increased. This may open many interesting questions. For instance, for efficient acceleration from 19 0MeV to 400 MeV the annular coupled structure (ACS) was applied with frequency jump from 324 MHz to 972 MHz. Upstream part of J-PARC linac from the frequency jump is set with the equi-partitioning (EP) condition, which prevents from the coherent resonances. If EP condition is kept for the downstream part, due to the frequency jump, the transverse focusing should also ‘jump' 3 times with shrink of envelop. The increased beam-density affects the interactions between particles, including the intra-beam stripping (IBS) effect in the H− beam. The temperature ratio between transverse and longitudinal planes is used as a knob for studying the beam behavior for the cases away from equi-partitioning. The IBS effects, as well as strategies for setting downstream non-equi-partitioning lattice due to frequency jump are studied. The matching and beam evolution in the transition section from EP to non-EP (MEBT2) are also studied. The results help to reach an optimum with least risks from resonances and IBS effects and so on.
MOP232	Optimization of the Superconducting Section of Injector Ⅱ for C-ADS	122
	S.H. Liu, Y. He, Z.J. Wang IMP, Lanzhou, People's Republic of China
	Abstract: The China Accelerator driven System (C-ADS) project which includes a high current SC proton linac is being studied under Chinese Academy of Science. Injector II, one of parallel injectors, is undertaken by Institute of Modern Physics (IMP). The lattice design of Injector II has been done. While in most case, the elements, such as SC cavities and SC solenoids, have different weight to the final beam parameters. What is more, in the real operation process of the machine, the optimized mode is hard to find. In the paper, Latin sampling method specified in DAKOTA code combined with TRACK is adopted to build hundreds of virtual machines to analyse the sensitivity of the SC section and to find optimization operation mode.
MOP233	Error and Tolerance Studies for Injector II of C-ADS	125
	W.S. Wang, Y. He, Z.J. Wang IMP, Lanzhou, People's Republic of China
	The proposed Chinese Accelerator Driven System (C-ADS) driver linac is being designed by Chinese Academic Science (CAS). Injector II is designed and fabricated in Institute of Modern Physics (IMP). Injector II will accelerate 10 mA proton beams to 10 MeV. Because of the high final beam power (100 kW) specified for the linac operation, beam loss must be limited to 10-5 level to avoid radiation damage. Misalignment and RF error simulation for cavities and focusing elements after RFQ were performed and the correction schemes developed using the computing code TRACK. Error and tolerance studies for Injector II are presented.
MOP235	Medium Energy Beam Transport Design Update for ESS	128
	I. Bustinduy, F.J. Bermejo, A. Ghiglino, O. González, J.L. Muñoz, I. Rodríguez, A. Zugazaga ESS Bilbao, Bilbao, Spain B. Cheymol, M. Eshraqi, R. Miyamoto ESS, Lund, Sweden J. Stovall CERN, Geneva, Switzerland
	The major challenge of this part of the accelerator is to keep a high quality beam, with a pulse well defined in time, a low emittance and a minimized halo, so that the beam losses downstream the linac be limited and the overall ESS reliability be maximized. In order to minimize beam loss at high energy linac, and the consequent activation of components, a fast chopping scheme is presented for the medium energy beam transport section (MEBT). The considered versatile MEBT is being designed to achieve four main goals: First, to contain a fast chopper and its correspondent beam dump, that could serve in the commissioning as well as in the ramp up phases. Second, to serve as a halo scraping section by means of two adjustable blades. Third, to measure the beam phase and profile between the RFQ and the DTL, along with other beam monitors. And finally, to match the RFQ output beam characteristics to the DTL input both transversally and longitudinally. For this purpose a set of ten quadrupoles is used to match the beam characteristics transversally, combined with two 352.2 MHz buncher cavities, which are used to adjust the beam in order to fulfill the required longitudinal parameters.
MOP243	Experimental Results of Beam Halo at IHEP	151
	H.F. Ouyang, T. Huang, J. Li, J. Peng, T.G. Xu IHEP, Beijing, People's Republic of China
	Space-charge forces acting in mismatched beams have been identified as a major cause of beam halo. In this paper, we describe the beam halo experimental results in a FODO beam line at IHEP. With this beam transport line, experiments are firstly carried out to determine the main beam parameters at the exit of a RFQ with intense beams, and then the measured beam profiles at different positions are compared with the multi-particle simulation profiles to study the formation of beam halo. The maximum measured amplitudes of the matched and mismatched beam profiles agreed well with simulations. Details of the experiment will be presented.
TUO3A01	Dynamical Aspects of Emittance Coupling in Intense Beams	240
	I. Hofmann GSI, Darmstadt, Germany I. Hofmann HIJ, Jena, Germany
	In this paper we study in an idealized lattice model the dynamical behavior of non-equipartitioned beams and of approach to equipartition. It is shown that emittance transfer depends on times scales of tune change, but also the direction of crossing the stopbands of space charge resonances. This provides additional information to support the stability charts suggested previously as design tool for high current linacs.
	Slides TUO3A01 [4.897 MB]
TUO3A03	Equipartition, Reality or Swindle?	250
	J.-M. Lagniel GANIL, Caen, France
	By way of introduction to a general discussion on space-charge induced energy equipartition (EQP), the following questions will be tackled: Why the formula presently used to define EQP is wrong? Why energy exchanges can occur although the EQP rule is respected? Why safe tunings can be find although the EQP rule is not respected? Why EQP is a swindle for a large majority of our accelerated beams? Why LINAC designers nevertheless like to use the EQP rule?
	Slides TUO3A03 [1.537 MB]
TUO3B01	Beam Dynamics Design of ESS Warm Linac	274
	M. Comunian, F. Grespan, A. Pisent INFN/LNL, Legnaro (PD), Italy I. Bustinduy ESS Bilbao, Bilbao, Spain L. Celona, S. Gammino, L. Neri INFN/LNS, Catania, Italy R. De Prisco Lund University, Lund, Sweden M. Eshraqi, R. Miyamoto, A. Ponton ESS, Lund, Sweden
	In the present design of the European Spallation Source (ESS) accelerator, the Warm Linac will accelerate a pulsed proton beam of 50 mA peak current from source at 0.075 MeV up to 80 MeV. Such Linac is designed to operate at 352.2 MHz, with a duty cycle of 4% (3 ms pulse length, 14 Hz repetition period).In this paper the main design choices and the beam dynamics studies for the source up to the end of DTL are shown.
	Slides TUO3B01 [17.664 MB]
TUO3B02	Beam Dynamics of the ESS Superconducting Linac	278
	M. Eshraqi, H. Danared, R. Miyamoto ESS, Lund, Sweden
	The European Spallation Source, ESS, uses a linear accelerator to deliver the high intensity proton beam to the target station. The nominal beam power is 5 MW at an energy of 2.5 GeV. The superconducting part covers more than 95\% of the energy gain and 90\% of the length. The beam dynamics criteria applied to the design of the superconducting part of the linac including the frequency jump at a medium energy of 200 MeV as well as the beam dynamics performance of this structure are described in this paper.
	Slides TUO3B02 [4.406 MB]
TUO3B03	Linac4 Beam Commissioning Strategy	283
	J.-B. Lallement, A.M. Lombardi, P.A. Posocco CERN, Geneva, Switzerland
	Linac4 is a 160 MeV H− ion linear accelerator, presently under construction, which will replace the 50 MeV Linac2 as injector of the CERN proton complex. Linac4 is a 90 m long normal-conducting Linac made of a 3 MeV Radio Frequency Quadrupole (RFQ) followed by a 50 MeV Drift Tube Linac (DTL), a 100 MeV Cell-Coupled Drift Tube Linac (CCDTL) and a Pi-Mode Structure (PIMS). Starting in 2013, five commissioning stages, interlaced with installation periods, are foreseen at the energies of 3, 12, 50, 100 and 160 MeV. In addition to the diagnostics permanently installed in the Linac, temporary measurement benches will be located at the end of each structure and will be used for beam commissioning. Comprehensive beam dynamics simulations were carried out through the Linac and the diagnostic benches to define a commissioning procedure, which is summarised in this paper. In particular, we will present a method for emittance reconstruction from profile measurements which keeps into account the effects of space charge and finite diagnostics resolution.
	Slides TUO3B03 [2.951 MB]
TUO3B04	End to End Beam Dynamics and Design Optimization for CSNS Linac	286
	J. Peng, S. Fu, H.C. Liu, H.F. Ouyang, X. Yin IHEP, Beijing, People's Republic of China
	The China Spallation Neutron Source (CSNS) will use a linear accelerator delivering a 15mA beam up to 80MeV for injection into a rapid cycling synchrotron (RCS). Since each section of the linac was determined individually, a global optimization based on end-to-end simulation results has refined some design choices, including the drift-tube linac (DTL) and the medium energy beam transport (MEBT). The simulation results and reasons for adjustments are presented in this paper.
	Slides TUO3B04 [1.131 MB]
TUO3B05	Beam Dynamics of the 13 MeV/50 mA Proton Linac for the Compact Pulsed Hadron Source at Tsinghua University	289
	Q.Z. Xing, X. Guan, C. Jiang, C.-X. Tang, X.W. Wang, H.Y. Zhang, S.X. Zheng TUB, Beijing, People's Republic of China J.H. Billen, J. Stovall, L.M. Young TechSource, Santa Fe, New Mexico, USA G.H. Li NUCTECH, Beijing, People's Republic of China
	Funding: Work supported by the Major Research plan of the National Natural Science Foundation of China (Grant No. 91126003) We present the start-to-end simulation result on the high-current proton linac for the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. The CPHS project is a university-based proton accelerator platform (13 MeV, 16 kW, peak current 50 mA, 0.5 ms pulse width at 50 Hz) for multidisciplinary neutron and proton applications. The 13 MeV proton linac contains the ECR ion source, LEBT, RFQ, DTL and HEBT. The function of the whole accelerator system is to produce the proton beam, accelerate it to 13 MeV, and deliver it to the target where one uniform round beam spot is obtained with the diameter of 5 cm.
	Slides TUO3B05 [7.715 MB]
WEO3B01	FRIB Accelerator Beam Dynamics Design and Challenges	404
	Q. Zhao, A. Facco, F. Marti, E. Pozdeyev, M.J. Syphers, J. Wei, X. Wu, Y. Yamazaki, Y. Zhang FRIB, East Lansing, Michigan, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661. The Facility for Rare Isotope Beams (FRIB) will be a new national user facility for nuclear science. This cw, high power, superconducting (SC), heavy ion driver linac consists of a frontend to provide various highly charged ions at 0.5 MeV/u, three SC acceleration segments connected by two 180° bending systems to achieve an output beam energy of ≥200 MeV/u for all varieties of stable ions, and a beam delivery system to transport multi-charge-state beams to a fragmentation target at beam power of up to 400 kW. The linac utilizes four types of low-beta resonators with one frequency transition from 80.5 to 322 MHz after Segment 1, where ion charge state(s) is boosted through a stripper at ≤20 MeV/u. The beam dynamics design challenges include simultaneous acceleration of multi-charge-state beams to meet beam-on-target requirements, efficient acceleration of high intensity, low energy heavy ion beams, limitation of uncontrolled beam loss to <1 W/m, accommodation of multiple charge stripping scenarios, etc. We present the recent optimizations on linac lattice, the results of end-to-end beam simulations with machine errors, and the simulation of beam tuning and fault conditions.
	Slides WEO3B01 [7.899 MB]
WEO3B02	Acceleration and Transportation of Multiple Ion Species at Ebis-based Preinjector	409
	D. Raparia BNL, Upton, Long Island, New York, USA
	A new heavy ion pre-injector at Brookhaven National Laboratory consist of an electron Beam Ion Source (EBIS), RFQ and IH Linac and a short transport line. This pre-injector provide any ion Helium to Uranium at energy of 2 MeV/u for Relativistic Heavy Ion Collider (RHIC) and the NASA Space Radiation Laboratory (NSRL). EBIS produces multiple charge states of an ion of interested. These charge states are accelerated through RFQ (300 keV/u) and IH Linac (2 MeV/u) and transported to booster. Charge desecration occurs just before the injection into the booster. This paper discusses implication of acceleration and transports of multiple charge state ions.
	Slides WEO3B02 [5.825 MB]
WEO3B03	PXIE at FNAL	414
	N. Solyak, C.M. Baffes, A.Z. Chen, Y.I. Eidelman, B.M. Hanna, S.D. Holmes, V.A. Lebedev, S. Nagaitsev, J.-F. Ostiguy, R.J. Pasquinelli, D.W. Peterson, L.R. Prost, G.W. Saewert, A. Saini, V.E. Scarpine, A.V. Shemyakin, D. Sun, V.P. Yakovlev Fermilab, Batavia, USA
	PXIE is the integrated systems test for the Project X frontend. It is expected to accelerate 1-2 mA CW beam up to 30 MeV. The major goal of the project is a validation of the Project X concept and elimination of technical risks. It is expected to be constructed in the period of 2012-2016. In presentation the conceptual design of the experimental test facility, lattice and beam dynamics studies will be discussed in details.
	Slides WEO3B03 [4.561 MB]
WEO3B04	RFQ Beam Dynamics Design for Large Science Facilities and Accelerator-Driven Systems	419
	C. Zhang IAP, Frankfurt am Main, Germany
	Serving as the front-end of large science facilities and Accelerator-Driven Systems (ADS), the Radio-Frequency Quadrupole (RFQ) accelerator usually needs to reach low beam losses, good beam quality, high reliability, and cost savings such design goals at high beam intensities. To address the challenges for modern RFQs, a special beam dynamics design technique characterized by a reasonable and efficient bunching process with balanced space-charge forces has been developed as an alternative to the classic Four-Section Procedure proposed by Los Alamos National Laboratory (LANL). In this paper, the design studies of some recent RFQ projects will be presented as examples.
	Slides WEO3B04 [3.698 MB]
WEO3B05	Using Step-Like Nonlinear Magnets for Beam Uniformization at IFMIF Target	424
	Z. Yang, J.Y. Tang IHEP, Beijing, People's Republic of China N. Chauvin, P.A.P. Nghiem CEA/DSM/IRFU, France
	Uniform beam distribution and minimum beam halo on target are often required in high intensity beam applications to prolong the target lifetime, ease cooling and obtain better irradiation effect. In this report, step-like nonlinear magnets instead of standard multipole magnets have been studied for the application at IFMIF. Although the preliminary results are still below the very critical requirement of spot uniformity at the IFMIF target, they are quite permissive. The method demonstrates significant advantages over the conventional combination of octupole and duodecapole on very low beam loss, better uniformity and very low cost. Further studies are needed to fully meet the IFMIF specifications.
	Slides WEO3B05 [1.487 MB]
THO3A01	High Intensity Aspects of J-PARC Linac Including Re-commissioning after Earthquake	497
	M. Ikegami, K. Futatsukawa, T. Miyao KEK, Ibaraki, Japan Y. Liu KEK/JAEA, Ibaraki-Ken, Japan T. Maruta, A. Miura, J. Tamura JAEA/J-PARC, Tokai-mura, Japan
	We had a massive earthquake in March 2011, which forced us to shutdown J-PARC accelerators for nearly nine months due to its resultant damages. After significant restoration effort, we resumed the beam operation of J-PARC linac in December 2011 and user operation in January 2012. Subsequently, we restored the same beam power as just before the earthquake in March 2012. In the course of the beam commissioning after the earthquake, we have experienced beam losses which were not observed before the earthquake. We discuss the experimentally observed beam losses and its comparison with particle simulations.
	Slides THO3A01 [5.249 MB]
THO3A02	Beam Dynamics of China ADS Linac	502
	Z. Li Private Address, Beijing, People's Republic of China P. Cheng, H. Geng, Z. Guo, C. Meng, B. Sun, J.Y. Tang, F. Yan IHEP, Beijing, People's Republic of China
	Funding: Supported by China ADS Program(XDA03020000), National Natural Science Fundation of China (10875099) and IHEP Special Fundings(Y0515550U1) An ADS study program is approved by Chinese Academy of Sciences at 2011, which aims to design and built an ADS demonstration facility with the capability of more than 1000 MW thermal power within the following 25 years. The 15 MW driver accelerator will be designed and constructed by the Institute of High Energy Physics (IHEP) and Institute of Modern Physics (IMP) of China Academy of Sciences. This linac is characterized by the 1.5 GeV energy, 10 mA current and CW operation. It is composed by two parallel 10 MeV injectors and a main linac integrated with fault tolerance design. The superconducting acceleration structures are employed except the RFQ. The general considerations and the beam dynamics design of the driver accelerator will be presented.
	Slides THO3A02 [5.822 MB]
THO3A03	Simulations and Measurements in High Intensity LEBT with Space Charge Compensation	507
	N. Chauvin CEA/IRFU, Gif-sur-Yvette, France O. Delferrière, R. Gobin, P.A.P. Nghiem, D. Uriot CEA/DSM/IRFU, France R.D. Duperrier ESS, Lund, Sweden
	Over the last years, the interest of the international scientific community for high power accelerators in the megawatt range has been increasing. One of the major challenges is to extract and transport the beam while minimizing the emittance growth in the Low Energy Beam Transport line (LEBT). Consequently, it is crucial to perform precise simulations and cautious design of LEBT. In particular, the beam dynamics calculations have to take into account not only the space charge effects but also the space charge compensation of the beam induced by ionization of the residual gas. The code SOLMAXP has been developed in CEA-Saclay to perform self-consistent calculations taking into account space charge compensation. Extensive beam dynamics simulations have been done with this code to design the IFMIF LEBT (Deuteron beam of 125 mA at 100 keV, cw). The commissioning of the IFMIF injector started a few months ago and emmittance measurements of H+ and D+ beams have been done. The first experimental results will be presented and compared to simulation.
	Slides THO3A03 [3.165 MB]
THO3A04	Beam Halo Definitions and its Consequences	511
	P.A.P. Nghiem, N. Chauvin, D. Uriot CEA/DSM/IRFU, France W. Simeoni CEA/IRFU, Gif-sur-Yvette, France
	In high-intensity accelerators, much attention is paid to the beam halo: formation, growth interaction with the beam core, etc. Indeed, beam losses, a critical issue for those high-power accelerators, directly depend on the beam halo behaviour. But in the presence of very strong space-charge forces, the beam distribution takes very different shapes along the accelerator, often very far from any regular distributions, with very varied halo extensions. The difficulty is then to find a general definition of the halo capable of describing any distribution type. This paper proposes a definition of the beam halo, studies its consequences and compares it to the most usual ones.
	Slides THO3A04 [9.030 MB]